Sending mails long delay

Infos:

  • Used Zammad version: 5.1.0-1647874663.58f3cd67.focal
  • Used Zammad installation type: package
  • Operating system: Ubuntu 9.4.0-1ubuntu1~20.04
  • Browser + version: Chrome v100

Sending mails from zammad-web with my pre-configured mail account takes forever to actual send. In my attempts I tried to send about 20-30 mails to various users using zammad.
The delay itself was always from 5 to 15 minutes. Receiving mails was not a problem at all. Sending mails from the mail account without zammad worked without a problem too.

So zammad must be struggling with something?

Expected behavior:

  • Sending mails without big delay

Actual behavior:

  • Sending mails takes forever to send them to their recipient.
  • Took about 5-15 minutes to send

Steps to reproduce the behavior:

  • Answering on any support ticket in zammad-web using the UI.